Utility meters are used for billing services provided by public utilities such as electricity, gas and water. For example, kilowatt-hour meters, located on a customer premise, include detachable meter units for measuring and recording electric power consumption by the subscriber. Typically, a kilowatt-hour meter is provided at each of the subscriber locations. A typical kilowatt-hour meter includes either a rotating disk or a completely electronic circuit that monitors the energy consumption within the subscriber location. Meter-reading personnel periodically inspect each subscriber site and record utility meter readings, either by hand or using an electronic probe to retrieve data stored in the solid state memory of the meter. Billing information is generated based upon the data collected by the meter reader.
Presently, utility meters are available that include interface equipment to permit remote interrogation of the meter and transmission of the collected usage data. The connectivity between the utility meters located at the subscriber site and the central billing facility can be provided using various different methods of communication, such as power line communication, dedicated signaling lines, the public telephone network or RF transmissions between meters and remote gateways in communication with the utility.
As a result of increased utilization of automatic remote reading of utility meters, there has been a decrease in the frequency of on-site inspection of metering equipment. The reduction in the number of actual physical visits to a customer site has increased the opportunities for undetected tampering with the metering equipment.
Presently, most single phase and polyphase electricity meters in the United States are socket mounted. The electricity meter includes a series of blade contacts that fit within a socket assembly, which allows the meter to be easily removed and replaced for servicing. However, the ease of removal and replacement also increases the likelihood that the meter can be removed from the meter socket and tampered with. One type of tampering with the meter is to remove the meter and reinstall the meter upside down, resulting in reverse rotation of the internal meter disk and register dials that record cumulative energy consumption.
Prior generations of electricity meters employed mechanical techniques to sense the installation of a meter and included a counter sealed beneath the meter cover that recorded and displayed the number of times the meter had been removed and reinstalled. Later generations of electricity meters employed mechanical tilt switches and logic elements to sense removal and/or reorientation of the meter.
Although mechanical switches have proven effective at sensing removal and reinstallation of the meter when the meter is reinstalled upside down, these techniques are not able to reliably sense meter removal from the socket when a reasonable attempt is made to maintain the meter in its normal orientation. Further, if the tilt switch is made overly sensitive, the system will falsely report tampering in response to normal events.
Therefore, a need exists for an improved tamper detection method that allows the meter to sense when the meter has been removed from the socket and relay information relating to the detected tampering back to the utility for remote sensing.